In the prior art, there are known devices for slot perforation of wells disclosed in Russian Federation Patents RU 2205941 C2, IPC 7 E21B 43/112, 10.06.2003; RU 2244806 C1, IPC 7 E21B 43/112, 20.01.2005; RU 2254451 C1, IPC 7 E21B 43/112, 20.06.2005; RU 2239053 C1, IPC 7 E21B 43/114, 27 Oct. 2004, containing cutting tools in the form of rolling disks. However, when using these devices, the formation of perforated slots is performed only in one projection, which leads to the necessity to reorient the perforator after forming each perforation slot, and to make additional round-trip operations.
In the prior art, there is known a more efficient double sided hydromechanical slot-type perforator according to Russian Federation Patent RU 2249678 C2, IPC 7 E21B 43/112, 10 Apr. 2005, which allows to perform the drilling-in of wells simultaneously with formation of two diametrically opposite slots in the production string, containing the casing with cutting tools mounted in it in the form of two discs and the mechanism of their extension. At that the diameter of the cutting disc of mentioned perforator is close to the diameter of perforator's casing that allows making perforation slots with a considerable depth.
The disadvantage of this device is a non-uniform force application on the cutting discs, in virtue of which the upper cutting disc during opening of the column goes beyond its dimensions to the maximum distance, while the lower disc during opening exercises drilling-in less effectively, and therefore the second slot formed by it may not reach required width and depth, and after prolonged use of the perforator and wear of the lower disc can be absent at all.
The mentioned shortcoming is overcome to some extent in a device according to the Patent EA 009905 B1, IPC E21B 43/112, 28 Apr. 2008, which is herein further referred to as a ‘prototype’.
The device according to the prototype is a hydromechanical slot-type perforator, comprising a casing with a piston-pusher placed in it and telescoping cutting tools in the form of cutting discs mounted on axes with the mechanism of their extension, with the possibility of cutting of two diametrically opposite slots, at that the drive mechanism includes a balance beams mounted on a central axis with cutting discs' axis installed in their arms, at that the balance beams are configured with the possibility of rotation when you move the piston-pusher, and jet nozzles, where the ratio of axial distances from the upper and lower cutting discs to the central axis is determined by the diameter of the column and equals 1.5-1.25.
The device, according to the prototype, due to an increase of axial distance from the lower cutting discs to the central axis provides a guaranteed yield of the lower exit out of production string and the formation of the second diametrically located slot by the lower cutting disk.
However, the prototype device has the following disadvantages:
1. Persisting uneven force application to the cutting disks: force of the piston is primarily applied to the upper blade, and only indirectly to the lower blade.
2. The same quality of column opening by means of both the cutting disks is not provided.
3. Discs are worn unevenly, that after prolonged use leads to an increase in the number of additional round-trip operations necessary to replace the disc.